This invention relates to a method and a switching router for simple scheduling of realtime data telegrams in calculable, load-insensitive cycle times.
Ethernets are being used increasingly today in the automation environment. An automation system requires a calculable response time. It must be certain that data can be transmitted within a defined period of time. Cycle time is one component of the response time in data transmission. When using an Ethernet, there is no primary calculability of the response time and/or cycle time. This is due to the fact that the basic regulating mechanism thereof functions according to a so-called “best effort” principle, which usually ensures good response times but is load dependent. In other words, at times of high communication traffic and/or when the volume of data to be transmitted is high, the response time can no longer be guaranteed.
There are various methods of bypassing this weakness in principle. As a rule, these methods tend to use special network components or the operation of standard Ethernet nodes is prohibited. However, this significantly limits the applicability and acceptance of this technique.
German patent application 100 58 524.8 discloses a method for transmission of data over switchable data networks, in particular an Ethernet in the field of industrial installations, in which realtime-critical and non-realtime-critical data are transmitted. According to the reference, the data are transmitted in a transmission cycle with an adjustable period, where each transmission cycle is subdivided into a first range for transmission of realtime-critical data for the realtime control and a second range for transmission of non-realtime-critical data. The German application discussed in this paragraph is incorporated into the present application by reference.